Closed-end resonating horn



Dec. 9, 1930. M R. HUTCHESQN CLOSED END RESONATING HORN Filed May 24, 1927 M I I VEN OR H BY .fiM/LLQ ATTORNEY Patented Dec. 9, 1930 UNITED STATES- PATENT OFFICE MILLER REESE HUTGHISON, OF PARK, WEST ORANGE, JERSEY, AS-

SIGNOR, BY MESNE ASSIGNMENTS, TO ACOUSTIC PRODUCTS COMPANY, OF NEW YORK, N, Y., A CORPORATION OF DELAWARE CLOSED-END BESONA'I'ING HORN Application filed m 24,

. This invention relates to sound generating devices, and, more particularly, to sound reresonating chambers may be tuned to a;

definite note of the chromatic scale and utilized for reproducing that particular note or various overtones or harmonics thereof. It is thus necessary to employ only twelve chambers resonant to the various notes in one octave of the chromatic scale in order to amplify and reproduce the entire range of musical frequencies.

Should an open end resonator be employed, the length thereof would be excessive due to the fact that such a device is resonant to a wave having a length only twice that of the pipe itself. This would be particularly noticeable if the device is made resonant to one of the lower' octaves and will cause'the arrangement to be unsuitable for private use amplifying the waves produced by a vibrating diaphragm. Since such-a pipe is resonant to a wave four times its own length it occupies only half the space required by an open end pipe which is resonant to the same note. A bank of twelve closed end pipes, each tuned to a definite note in the chromatic scale, and energized by a suitable diaphragm, may consequently be employed for the reproduction of the various notes comprising a complete scale.

In accordance with this invention, a pipe having a closed end is utilized as a resonator associated with the diaphragm of an electromagnetic unit. The diaphragm is analogous toatuning fork and sets'up waves of compressions and rarefactions in the pipe, which, if

19527. Serial No. mama.

they are of the fre uency to which the pipe is resonant, are amp ified and impressed upon the surroundin nators are emp oyed which are tuned respectively to the several notes comprising an octave in the chromatic scale. vices are capable of amplifying the various overtones of their fundamental fre uency but are relatively inca able. of repro ucin notes of lower frequencles, it is usually pre erable to tune the resonators to the lowest octave it is desirable to reproduce. Their fundamental frequency and the various overtones will then comprise the complete musical scale, and any notes of lower frequency which may be present will be largely suppressed.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be specifically pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization, may be better understood by referring to the following description taken in. connection with the accompanying drawing forming a part thereof, in which like reference characters have been used to denote like parts in the various figures. is, however, primarily for purposes of disclosure, it will be understood that the structure and the method of operation thereof may be modified in various respects without departing from the broad spirit and scope of the invention.

One embodiment of the invention has been shown for purposes of illustration inthe accompanying drawing,in which Fig. 1 illustrates a closed end resonator constructed in accordance with this invention;

Fig. 2 is a front elevation of a bank of such resonators, and

Fig. 3 shows a modification thereof in which the vibrating diaphragm is located at one end of the pipe.

In the following description and in the claims the various parts of the apparatus and medium. Twelve such reso- Since the de- Since such illustration details of the invention will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit.

Referring to the drawing more in detail, and in particular to Fig. 1, the pipe 1 is shown having one end closed and the other end T-shaped. Electromagnetic reproducing unit 2, which may be of any well known form having movable diaphragm 3, is secured to one side of the T-shaped end, and the opposite side thereof may be provided with a hell or horn 4. Vibrations of the diaphragm in response to applied pulsating electric currents cause compressions and rarefactions in the air within the tube, which travel outwardly as sound waves. If the waves are of a frequency to which the pipe is resonant they will set up vibrations within the pipe and be re-enforced thereby for producing a strong musical note.

Fig. 2 illustrates a plurality of pipes 1 and co-operating electromagnetic units 2 for imparting sound waves thereto. Pipes 1 are of different lengths and are tuned to different frequencies. Preferably a bank of twelve such units should be employed each unit being tuned to a different note in the chromatic scale as will be hereinafter explained.

In the modification shown in Fig. 3, the various elements are similar to those disclosed in Fig. 1, and are given the same reference numerals. The electromagnetic unit 2, however, is located across the end of pipe 1 instead of at the side thereof. In this case, the diaphragm is located directly over the air column and bell 4 is mounted at right angles thereto.

In the operation of the above described device, waves of a length four times that of the air column in tube 1 will be most strongly re-enforced and amplified. Operation is in this respect similar to that of a tuning fork which is spaced above a closed air column and produces air waves comprising rarefactions and compressions which are reflected by the closed end of the column, and re-enforced. The action of resonator is selective as to waves of its own fundamental frequency and overtones or harmonics thereof. Waves of other frequencies and particularly those of a frequency lower than a fundamental are re-enforced but slightly, consequently in the resulting note emitted the ratio of the amplitude of the waves of desired frequency to those of other freqencies is considerably increased.

A bank of such resonators is preferably employed each individual unit being tuned to a definite note of the chromatic scale comprising a predetermined octave. If the selected octave is the lowest which it is desired to reproduce, the device will amplify notes over the entire musical range and suppress other noises.

The invention therefore provides a means for efficiently producing sound waves corresponding to musical notes and for emitting such waves with a minimum amount of distortion and interference. The device is furthermore constructed to occupy a. minimum amount of space. As a result, the entire chromatic scale, with its overtones and barmonies, may be reproduced by an instrument having theoretical' as well as practical purity of tone from a small and compact unit which may be installed in a single appropriate cabinet and can be installed at any convenient location such as a private home, where compactness is a prime requisite. The bells may, of course, be of relatively large size permitting the use of the apparatus in large halls and audito-riums where a large volume of sound is desirable, since the diaphragm from the closed resonator may be sufiiciently elastic to produce the appropriate sound waves in a comparatively lar e bell.

While certain novel features of t ie invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation may be made bythose skilled in the art without departing from the spirit of the invention.

What is claimed is:

' 1. In an acoustic device, a tube closed at one end and having an opening at the other end, said opening having a flaring horn applied in communication therewith, and means in said tube adjacent said opening for generating sound waves.

2. In an acoustic device, a tube closed at one end and having an opening in the side wall at the other end, a diaphragm in the wall of said tube opposite said opening, and a source of sound waves in operative relationship to said diaphragm.

3. In an acoustic device, a tube closed at one end and having an opening in the side wall at the other end, said opening having a flaring horn applied in communication therewith, means in the wall of said tube opposite said opening for generating sound waves.

4. In an acoustic device, a tubeclosed at one end and having an opening in the side wall at the other end, said opening having a flaring horn applied in communication with said opening, means in the side walls of said tube adjacent said opening for generating sound waves.

Signed at New York, in the county of New York and State of New York, this 20 day of May. A. D. 1927.

MILLER REESE HUTCHISON. 

